Wiktor Wise
In-lens detectors are a type of secondary electron detector used in scanning electron microscopes (SEMs) to collect secondary electrons (SEs) and form images. They are located in line with the field emission gun, perpendicular to the surface of the sample. In-lens detectors utilize low acceleration voltage and a decelerating electric field to collect near-axial backscattered electrons (BSEs) with high angular aperture. The design of the in-lens detector allows for the detection of low-energy SEs, providing useful information for profiling membrane nanostructures and improving image resolution in biological samples.
| Characteristics | Values |
|---|---|
| Detector design | Based on the standard in-lens detector used in FEI SEMs |
| Function | Collects BSEs that reach the objective lens but have a high emission angle |
| Contrast and resolution | Affected by the interaction volume and the signal from the surface layer of the sample |
| Signal | The InLens detector is located in line with the field emission gun, perpendicular to the surface of the sample |
| Imaging | Enables imaging with LLE using simple high-pass filtration |
| Efficiency | Depends on the electric field of the electrostatic lens |
| Acceleration voltage | Utilizes low acceleration voltage or reduction of energy in front of the sample using a decelerating electric field |
| Spot shape | Increased due to the effect of aberrations and diffraction |
| Sample tilting | Cannot be used with sample tilting due to the effect on the emission angle of electrons |
| Radiation damage | Higher radiation damage to the sample compared to other techniques |
| Energy window | Can range from 100 eV to 10 eV with reasonable collection efficiency |
| SE detection | Detects SEs and BSEs |
| Photomultiplier | Converts light information into an electronic signal |
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What You'll Learn
- InLens detectors are used in electron microscopes to collect backscattered electrons (BSEs)
- The InLens detector is located in line with the electron source, perpendicular to the sample surface
- InLens detectors can be used for high-contrast topography or compositional contrast examinations
- InLens detectors can be used to image metal nanostructures of various sizes and geometries
- InLens detectors are more sensitive than Everhart-Thornley detectors, resulting in higher-resolution images
InLens detectors are used in electron microscopes to collect backscattered electrons (BSEs)
The InLens detector is located in line with the field emission gun, perpendicular to the surface of the sample. The InLens detector is designed to detect BSEs with high emission angles that intersect the axis far from the lower pole piece of the objective lens. These BSEs have a much higher angular aperture, resulting in greater spherical aberration.
The InLens detector is particularly useful for imaging biological samples, as it can improve resolution by reducing the effect of the large interaction volume of BSEs. This is achieved through the use of simple high-pass filtration, which separates the BSEs from the surface layer of the sample, allowing for clearer imaging.
Additionally, the InLens detector can be used in conjunction with other detectors, such as the Everhart-Thornley detector, to enhance the contrast and composition information obtained from the sample. By combining the topographical information from the InLens detector with the density data from the backscattered electron detector, detailed density-dependent colour SEM images can be created.
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The InLens detector is located in line with the electron source, perpendicular to the sample surface
The InLens detector is a secondary electron (SE) imaging technique used in scanning electron microscopes (SEMs). It is positioned in line with the electron source, at a 90-degree angle to the sample surface. This is in contrast to the standard SE detector, which is positioned at an angle relative to the electron source to obtain topographical information about the sample surface.
The InLens detector's position allows it to collect SEs and backscattered electrons (BSEs) with high efficiency. SEs are generated by inelastic collisions, in which they gain sufficient energy to overcome the work function of the material. They come from a thin layer close to the specimen surface, and their image provides topographic contrast. BSEs, on the other hand, are electrons from the primary beam that are scattered back by elastic or inelastic interactions with the sample's atomic nuclei. The BSE image provides material contrast, but the interaction volume depends on the primary beam energy, with higher energy resulting in deeper penetration.
The InLens detector utilizes the fact that near-axial BSEs follow a similar trajectory to the primary electrons but in the opposite direction. These BSEs have a higher angular aperture, resulting in higher spherical aberration. The InLens detector can detect these electrons as they intersect the optical axis after entering the objective lens.
The InLens detector's design includes several auxiliary electrodes that help direct electrons towards the detector. By adjusting the intensity of the electrostatic and magnetic fields, the detector's preferences can be altered, particularly regarding the energy of the detected electrons and the emission angle. This allows for the detection of both SEs and BSEs, providing a wide range of electron detection capabilities.
The InLens detector is a valuable tool for imaging nanostructures and biological samples, offering high-resolution images and the ability to separate different types of information generated by the primary electron beam.
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InLens detectors can be used for high-contrast topography or compositional contrast examinations
InLens detectors are used in scanning electron microscopes (SEMs) to collect signal electrons emitted from samples. They are positioned in line with the field emission gun, perpendicular to the surface of the sample. This geometric position allows InLens detectors to detect secondary electrons directly from the surface of the sample.
InLens detectors can also be used in conjunction with energy filtering to highlight specific sample properties. By filtering detected electrons, the contrast of the image can be changed, revealing new topography and material information. This technique is especially useful when observing a combination of multiple materials.
Furthermore, InLens detectors enable imaging with Low-Loss Electrons (LLE) using simple high-pass filtration. The electrostatic energy filter consists of a simple filtering grid and an additional pair of focusing electrodes that form the filtered electron beam in front of the mesh to increase its transmissivity. This technique reduces the effect of the large interaction volume of backscattered electrons (BSEs), improving the image quality.
Overall, the InLens detector's ability to detect secondary electrons directly from the sample surface, its sensitivity to SE1 electrons, and its compatibility with energy filtering make it a valuable tool for high-contrast topography and compositional contrast examinations.
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InLens detectors can be used to image metal nanostructures of various sizes and geometries
In-lens detectors are a type of secondary electron (SE) detector used in scanning electron microscopes (SEMs). They are located in line with the field emission gun, perpendicular to the surface of the sample. This distinguishes them from standard SE detectors, which are positioned at an angle relative to the electron source. In-lens detectors are used to image metal nanostructures of various sizes and geometries, providing useful information for profiling membrane nanostructures.
In-lens detectors work by collecting backscattered electrons (BSEs) that get to the objective lens but have such a high emission angle that they intersect the axis as far as 10 to 15 mm from the lower polepiece of the objective lens. This intersection occurs due to the effect of spherical aberration. The in-lens detector's design is based on the standard in-lens detector used in FEI SEMs. It utilizes low acceleration voltage, or a reduction of the energy immediately in front of the sample using a decelerating electric field just before the sample (deceleration mode) or inside the objective lens.
In-lens detectors have been used to image metal nanostructures of various sizes and geometries. For example, in a study by Griffin (2011), in-lens detectors were used to image metal nanostructures on insulating borosilicate glass using electron beam lithography. The study found that the relative measurement error depended on the acceleration voltage and the type of secondary electron detector used for imaging. In particular, Everhart-Thornley detectors' lower sensitivity to SE1 electrons increased the magnitude of shrinkage by up to 10% relative to in-lens measurements.
In-lens detectors have also been used to image nanostructures on recrystallized tungsten. This study examined the correlation between blisters and nanostructures with grain orientation. Three kinds of typical nanostructures were observed, with a clear dependence on grain orientation: triangular structures were observed on grains oriented near the 〈1 1 1〉 corner of the inverse pole figure, with lamellar structures formed for grains oriented near the 〈0 1 1〉 corner, and spongy structures for grains near the 〈0 0 1〉 corner.
In-lens detectors are a valuable tool for imaging metal nanostructures, providing high-resolution images and useful information for profiling membrane nanostructures. They are simple in construction and can be used to investigate the influence of scan direction and secondary electron detectors on imaging.
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InLens detectors are more sensitive than Everhart-Thornley detectors, resulting in higher-resolution images
The Everhart-Thornley detectors' lower sensitivity to SE1 electrons increases the magnitude of the shrinkage of up to 10% relative to InLens measurements. The InLens detector collects BSEs that reach the objective lens but have such a high emission angle that they intersect the axis as far as 10-15 mm from the lower pole piece of the objective lens due to the effect of spherical aberration.
InLens detectors are also used to investigate the effect of scan direction and secondary electron detectors on imaging. The relative measurement error depends on the acceleration voltage and the type of secondary electron detector used for imaging. In order to obtain high-resolution images from any scanning beam microscope, it is necessary to produce a small probe, have a small interaction volume in the substrate, and collect a large number of information-rich particles.
The InLens detector's sensitivity to SE1 electrons and its ability to collect a large number of information-rich particles contribute to its higher resolution compared to Everhart-Thornley detectors. The InLens detector's location and design, combined with its ability to collect BSEs with high emission angles, further enhance its sensitivity and imaging capabilities.
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